Orally administered pharmaceutical preparations are traditionally presented in the form of tablets, capsules, caplets, and the like, whether in ordinarily or sustained-release form. Such oral dosage units may, however, be difficult for certain patients to swallow because of their size and shape. In addition, the coatings conventionally used on traditional oral dosage units may themselves have an unpleasant taste or texture or may dissolve quickly upon contact with saliva in the mouth, causing the frequently bitter or unpleasant taste of the active pharmaceutical ingredient contained in the dosage unit to be sensed. Such factors may act as serious deterrents to the taking of medication by certain individuals, particularly children, mentally incapacitated patients and, in the case of veterinary preparations, small animals.
Various modified oral dosage units have been proposed in the prior art in an attempt to overcome the taste and swallowing problems associated with conventional dosage forms.
For example, in U.S. Pat. No. 3,922,379, orally active erythromycin derivatives were microencapsulated by suspending particles of said derivatives in water containing a water-soluble albumin and then stirring such suspension into a mixture of a liquid alkane and a non-ionic surfactant. The resultant microcapsules reportedly were effective in concealing the notoriously bitter taste of the erythromycin.
U.S. Pat. No. 3,919,436 discloses the use of a polymer containing as an essential component a substituted acrylamide as a coating substance for pharmaceutical tablets and granules.
U.S. Pat. No. 4,001,390 discloses a more complex coating system for solid dosage forms comprising an undercoat of a polymeric substance, a secondary coat consisting of a polymeric substance and a pigment, and a third or finish coat composed substantially of a polymeric substance.
The foregoing techniques for providing taste concealing coatings for oral dosage units are relatively complex and expensive for broad commercial use and may inhibit rapid dissolution (or smooth sustained release, in the case of sustained-release dosage forms), delaying the effective onset of the desired pharmaceutical activity. Moreover, the aforementioned prior art coating methods and substances do not significantly facilitate the swallowing of the oral dosage units and, thus, provide little advantage to patients who have difficulty in swallowing such medications.
In my recently issued U.S. Pat. No. 4,708,867, I disclosed a dosage form of the steroids prednisone and prednisolone which comprised an aggregate of minipellets contained within an ingestible capsule or other openable container. Each of the minipellets comprised the active drug coated on a nonpareil seed and surrounded by a layer of a copolymer of dimethylaminoethyl- and methylmethacrylate. Said minipellets were effective in concealing the unpleasant taste of the steroids and could be swallowed directly from the opened container, avoiding the problems associated with the swallowing of larger dosage units. Even these minipellets, however, suffer from certain drawbacks, including the difficulty in their manufacture resulting from the tackiness of the polymer coating.